Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are typically inserted through an insertion opening of an ink loader for the printer, and the ink sticks are pushed or slid along the feed channel by a feed mechanism and/or gravity toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium.
One difficulty faced in solid ink technology is identification and authentication of ink sticks to ensure the correct loading and compatibility of an ink stick with the imaging device in which it is used. For example, unlike powdered or liquid marking materials, the solid form of ink sticks allows the ink sticks to be handled and loaded into a phase change ink printer without the need for a container or cartridge, as is typically required for liquid ink or powdered toner. In addition, the entire ink stick may be melted and consumed, with no need to dispose of, or recycle, any container. Eliminating the need for a container provides many advantages to the use of ink sticks. Containers or cartridges, however, may be provided with electronic tags, barcodes, etc. that may be used to identify and/or authenticate the ink contained therein. Without the use of a container, the mechanisms for authenticating or otherwise identifying the ink stick may be limited.
Provisions have been made to facilitate the authentication and/or identification of ink sticks so that ink sticks are correctly loaded into the intended feed channel and to ensure that the ink sticks are compatible with the printer with which they are used. One provision is generally directed toward excluding wrong colored or incompatible ink sticks from being inserted into the feed channels of the printer. For example, the correct loading of ink sticks has been accomplished by incorporating keying features into the exterior surface of an ink stick. These features are protuberances or indentations that are located in different positions on an ink stick. For example, FIG. 9 shows an embodiment of an ink stick 2 that includes a keying feature 4 that is in the form of a notch that extends along a side surface of the ink stick. Corresponding key elements 6 are positioned on the perimeter of the opening 8 through which the ink stick 2 is inserted. An ink stick that does not have the appropriate key elements in the correct position for the particular insertion opening is excluded from insertion.
To further aid a customer in identifying ink sticks, previously known ink sticks have incorporated visually recognizable symbols either into a surface of the ink stick or as the shape of the ink stick itself. The visually recognizable symbol is a shape that provides the printer operator with meaning that the operator can then use to associate the ink stick with a particular keyed opening or feed channel. The printer operator can correlate a visually recognizable symbol with a particular feed channel more easily than correlating a keyed shape that does not convey symbolic significance.
The previously known ink sticks that incorporated visually recognizable symbols, however, have generally been cube shaped or have had longitudinal dimensions that are not substantially different from the width dimension of the ink stick. Emerging phase change ink jet technologies have reduced the time for generating solid ink images, and, as a result, have a high ink consumption rate. As a consequence, larger capacity solid ink delivery systems have been devised. The increased capacity of solid ink delivery systems having non-linear feed channels has prompted the development and use of ink sticks having a larger length to width aspect ratio. The use of “longer” ink sticks lessens the frequency at which the solid ink in the ink delivery system has to be replenished. Ink sticks that are generally larger in size and, in particular, longer in longitudinal, or length, dimension of the ink stick, however, may make visually recognizable symbols that encompass most or all of a surface or perimeter shape of the ink stick unrecognizable.